The present invention relates to a connector used for connecting circuits with each other in an electronic apparatus, and more concretely speaking, to a method for fabricating a multi-pin connector by terminal insert molding, in which a plurality of terminal rows, each row including a number of pin-shaped terminals, are juxtaposed closely to each other.
Recently down-sizing of electronic apparatuses such as OA apparatuses, AV apparatuses, communication apparatuses, personal computers, etc. advances and it is a matter of course that down-sizing and increase in number of pins (terminals) are required for a connector connecting different independent parts such as driving sections, memories, in/output sections, interfaces, displays, etc. therein. In order to deal with troubles taking place in the circuits, they are divided into several zones so that only troubled parts of the circuits can be exchanged, these zones being connected through connectors. In this way, it is possible to improve production yield by means for preventing influences of the troubles in a part on the whole of the apparatus. Consequently a small size connector is required, in which a number of pins (terminals) capable of dealing with such circuits are closely arranged, e.g. there are 24 pins arranged with a pitch smaller than 2.5 mm in parallel rows, which are arranged with an interval smaller than 0.8 mm.
As means for arranging closely a number of terminals in such a small region, terminal insert molding is applied thereto by injection molding using mold resin material such as engineering plastic, etc. However different terminals implanted in a connector by insert molding should be electrically independent from each other. For this purpose honeycomb-shaped dies of high precision are required, in which partition walls are disposed, which can hold a number of independent fine pins (terminals) separately from each other in predetermined positions close to each other. However such dies are expensive and much work is required for inserting the number of fine pins (terminals) independently into holes formed by the partition walls. Even if an automatic mounting machine is used therefor, increase in equipment investment and running cost is inevitable.
On the other hand, a thin terminal table die is simple, by which a plurality of terminals arranged in parallel with a small interval are formed by forward transfer press and extending perpendicularly from a terminal carrier and only a plurality of terminals included in a transversal hoop, whose plate surface is disposed transversally along a parting plane of the thin terminal table die, are inserted into a cavity in the die for a thin terminal table to be formed. By means thereof it is easy to effect the formation efficiently with a low cost. Consequently it is usual that a plurality of such one-row terminal tables are superposed on each other to bring them together in one socket in order to construct a multi-pin connector of one body.
However, although the die is simplified and insertion of terminals is easy for the multi-layered multi-pin connector, it requires mounting work and suitable linking members. The different linking members and a socket for bringing the linking members together hinders the down-sizing. Further, if a zigzag terminal arrangement is included in order to secure insulation between the different terminals in a small space, fabrication steps are complicated. Therefore, it is difficult to say that superposition of one-row terminals is always the best approach. For this reason, it is desirable to arrange a plurality of hoops, each having-a plurality of terminals formed by forward transfer press, with a small interval in parallel so that surfaces thereof are parallel to each other. This allows simultaneous insertion of a plurality of rows into the cavity in the terminal table die to effect terminal insert molding.
However, in order to support the hoops, to lead the terminals formed in hoops, and to shut closely the cavity in a lower side die by a stripper plate of an upper side die effecting the terminal insert molding, insert holes should be formed in the stripper plate so that different terminals juxtaposed on one hoop and separated by a predetermined small distance are isolated from each other. In this way, it is inevitable that the stripper plate has a construction, which is as complicated and expensive as the insert die using terminals separated from each other, described above.
An object of the present invention is to provide a method for fabricating a multi-pin connector having a small size and a high precision. The method utilizes terminal insert molding by means of simple dies by making hoops formed by a forward transfer press cooperate with a stripper plate.
In order to achieve the above object, a method for fabricating a connector for an electronic circuit by terminal, insert molding according to the present invention is one, by which a plurality of terminals are inserted simultaneously in a vertical direction through an opening in an upper surface into a cavity in a connector terminal table die. Each of band-shaped conductive thin plates is provided with a terminal carrier, which is cut away after the insert molding along its longitudinal direction, and a plurality of terminals extending in a direction perpendicular to a side of the terminal carrier therefrom and arranged in parallel to each other with a predetermined interval.
Slots engraved in a parting plane of the stripper plate have a width that is slightly greater than the thickness of the thin plates so that the plates are closely engaged with the slots. The terminals juxtaposed on the band-shaped conductive thin plates are positioned perpendicular to the upper surface of the, cavity. The terminal side end surface of the terminal carriers is aligned with the open ends of the slots on the parting plane. In this way, the open ends of the slots are completely filled by the terminal carriers. The parting plane is a flat continuous surface so that the cavity is shut closely by the parting plane.
Further the plurality of terminals are linked with the terminal side end surface of the terminal carrier through means, which can be easily broken by forced plastic deformation by bending so that the terminals are separated from the terminal carrier. The terminal carrier and the terminals are cut away from each other after the insert molding of the terminals so that the plurality of terminals, which were linked with each other through the end surface of the terminal carrier, are made independent from each other.
The plurality of slots are engraved in the stripper plate and the plurality of band-shaped conductive thin plates are arranged so that the width direction of the plate surfaces is vertical and that they are parallel to each other with a predetermined interval. In this way the slots can be charged with the terminal carriers in parallel. In addition, the band-shaped conductive thin plates arranged in parallel are located so that terminals of a plate are shifted with respect to corresponding terminals of another plate adjacent thereto by a predetermined distance in the longitudinal direction. In this way a terminal arrangement in zigzag in a transversal direction can be formed. Further it is desirable to form positioning holes in a terminal carrier part of each of the band-shaped conductive thin plates.
Each of the band-shaped conductive thin plates is 0.1 to 0.3 mm thick and as the means easily broken the width of linking portions linking each of the terminals on both the sides with a terminal side end surface of the terminal carrier is kept below 0.1 mm. A width of the linking portions is preferably 0.06 mm. For each of the band-shaped conductive thin plates a hoop is used, in which the plurality of terminals are formed by forward transfer continuous press.
The opening is shut closely by the stripper plate or metal die (hereinbelow, called simply die plate) during simultaneous insert molding of the plurality of terminals effected through the opening formed in the upper surface of the cavity in the connector terminal table die, using a plurality of longitudinal hoops, the width direction of plate surfaces of which stands vertically. A plurality of slots are engraved in the parting plane of the die plate for guiding terminal carriers, each of which is obtained by forming a plurality of terminals successively on a hoop by, forward transfer continuous press. A part of the parting plane removed by engraving the plurality of slots is filled with end surfaces in the thickness direction of the terminal carriers.
The opening in the upper surface of the cavity is shut closely during the insert molding by the parting plane complemented by the end surfaces in the thickness direction of the terminal carriers in order to prevent outflow of the resin. The terminal-carriers are removed after the insert molding so that the different terminals are isolated from each other. Two extremities of each of the slots in the longitudinal direction are opened so that the terminal carriers of the hoops can be passed continuously through the slots in the longitudinal direction, sliding therein.